The present invention relates to improvements in receiving and control means for shuttles in looms, more particularly looms of the gripper shuttle type in which the shuttle is picked alternately from both sides of the loom. Each time that the shuttle is picked from one side of the loom it must be braked on the opposite side of the loom at a location within the shuttle receiving mechanism. The shuttle must then be precisely positioned at a predetermined location for a threading operation and for accurate picking out of the receiving mechanism. If the shuttle is not precisely positioned, the amount of force transmitted to the shuttle by the picking mechanism will vary and this will result in an inaccurate shuttle flight, which in some cases may be insufficient so that the shuttle will not make it all the way to the opposite side of the loom.
It has been known in the weaving art to positively position a shuttle which has been received into the shuttle box so that it is in a predetermined position for threading and picking. However, the mechanism for braking or checking the shuttle and for positioning the shuttle must be disengaged from the shuttle at the time of picking. Just prior to the time of picking, there exists a possibility of losing control of the shuttle whereby external forces may cause the shuttle to move out of the predetermined picking position. This problem is particularly acute in looms which operate with a shuttle box which is turned 180.degree. after receiving the shuttle so that it can be picked out of the shuttle box to the opposite side of the loom. This type of loom is shown in the following U.S. patents to V. Svaty: No. 3,315,709 dated 25 Apr., 1967 and No. 3,330,305 dated 11 July, 1967 and No. 3,875,974 issued Apr. 8, 1975 to Rambousek. In the loom disclosed in these two U.S. patents, the gripper shuttle enters the shuttle box and is checked or braked. The filling which has been brought across the loom from the opposite side is disengaged and a new filling is inserted into the shuttle. The shuttle box is mounted on a turntable which is partially rotated after the new filling has been inserted into the shuttle box so that the shuttle is turned 180.degree. so that the head of the shuttle points towards the end from which it came. At this point, the braking or checking mechanism is released from its checking function on the shuttle and the shuttle is propelled or picked out of the shuttle box. See, for example, the braking mechanism disclosed in the Svaty et al patent U.S. Pat. No. 3,487,860 dated 6 Jan., 1970. As is shown in this last patent, the braking pressure must be relieved before the shuttle is picked. It is at this point between the time the brake is released and before the shuttle is picked that there is a tendency for the shuttle to be moved out of position by the newly inserted filling which is under tension. Any slight movement of the shuttle at this point will pull it toward the shed away from the picking mechanism. This will result in a faulty pick.
The type of loom to which the present invention is applied further includes pneumatic means for picking the shuttle. The pneumatic means comprise a piston to which is attached a picking member which engages the end of the shuttle. If the shuttle is not properly positioned close to the end of the picking member, the end of the shuttle will be struck abruptly thereby producing a high initial acceleration which in turn causes the filling to break. In addition, there may be less than a full transfer of energy from the picking member to the shuttle so that the shuttle may not be picked entirely through the shed or boxed properly on the opposite side of the loom.
Further refinements to the loom disclosed in the above identified patents have included the addition of positioning mechanism which places the shuttle in the proper position after it has been checked. However, even this mechanism has to be disengaged from the shuttle before the shuttle is picked, thereby leaving the shuttle under the influence of the filling which has just been inserted into the shuttle.